1. Technical Field
This invention relates to a coated type of magnetic recording media such as various magnetic tapes or various floppy disks.
2. Background Art
Various magnetic recording media including on a nonmagnetic support substrate a coated type magnetic layer obtained by dispersing ferromagnetic powders in a binder are generally used. In order to achieve an improvement in the recording density, however, it is naturally necessary to record high-frequency signals having short recording wavelengths. This, however, makes a lowering of the reproduction output unavoidable.
In order to prevent such an output drop, it is necessary to bring a medium in as microscopically close contact with the associated head as possible, thereby reading signals from the medium with a reduced spacing loss and without waste. For this purpose, the magnetic layer is required to be much more smoothed on its surface than ever before. However, smoothing the surface of the magnetic layer gives rise to an increase in the area of contact of the magnetic head with the medium, which in turn makes their coefficient of friction too large to disturb the stable running of the medium and decrease the wear resistance of the medium or head.
It has been known so far in the art that improving the running stability of a magnetic recording medium is achieved by adding various lubricants to the magnetic layer, thereby lowering the coefficient of friction. However, excessive use of the lubricants so as to improve the surface slip characteristics of the magnetic layer causes the magnetic layer to bloom out on the surface, rendering the running of the medium unstable, permits the associated magnetic head to be clogged up, dusted or otherwise have trouble, and gives rise to output and S/N ratio drops. When the amounts of the lubricants added are too small, on the other hand, their lubricating action becomes insufficient, failing to improve the running characteristics of the medium. Thus, not only is it very difficult to use the magnetic recording medium, but much difficulty is involved in designing it.
Apart from this, it has been known to use an MT class of low-structure carbon black so as to achieve a lowering of the coefficient of friction (JP-P-1-32573, JP-Kokai-58-133626, etc.).
However, such carbon black having a large particle diameter in a matter of 200 m.mu.m have been found to be less effective, because its unfavorable dispersibility gives rise to considerable output and S/N ratio drops.